Light-projecting device



May 7, 1929 A -H. L. cooks Y 1,712,027

LIGHT PROJECTING DEVICE Filed May 5, 1921 2 Sheets-Sheet 1 77 f EL 76 INVENTH .4 TTURNEYS May 7, 1929. H 1 COOKE 1,712,027

LIGHT PROJECTING DEVICE Filed May 3, 1921 2 Sheets-Sheet 2 B Y QM ,m l

Q A TTUHNEYS Yllllateiifteacll May 7, i929.

T OFFIC EEEEWEEE EEs'rEE COOKE, CE PRINCETON, NEW JERSEY, nssieNoE To COOKE Per ENrs iNCOEEOEATED, OE NEW YORK, N. Y., n CORPORATION CE DELAWARE.

LieJHT-rEoJEC'riNe DEVICE.

.Application filed. May 3,

This invention relates to light projecting devices and has for its primary Object to provide a device of the above mentioned character in which the source-of light proper is fixed at a definite point, such as the focal point, relative to the reflector or` other device for projecting the light.

This is notftrue of the devices heretofore usual, particularly such as employ incandescent electric lamps as sources of light, because the filament-s of different lamps are not at cxactly the same position relatively to the sockets, so that as the various lamps are placed into the sockets, the direction of the-beain -of light changes. In'many instances, however, 4it is exceedingly important that the direction 'of the beam remain unchanged, as for example, in railway signaling and in automobile headlights, in which latter instance the beam should be directed to the ground and not exceed a definite elevation in order to prevent glare.

In the present invention I propose to fix the filament absolutely in position relatively to the reflector and in the particular embodiment of the inventionhereinafter described, I propose to employ part of the bulb surface itself as a reflector, this lpart of the surface being shaped substantially like a paraboloid at the focus of which is placed the lamp filament or other source of light. I propose furthermore to provide inside the bulb a shield which serves to permit only the reflected light to pass out of the bulb. This shield may, however, be made of colored or translucent rather than opaque substance so as to permit part of the direct rays to pass therethrough and out of the bulb. This light,

however is so reduced in intensity as to prevent glare.`4

A good understanding of the invention may be had `from the following description of certain specific forms o`f the embodiment thereof, reference being had to the accompanying drawing, in which:

lio

Fig. 1 is a view partly in section, shou-l ing one form of embodiment of the invention;

Fig. 2 is a view similar to Fig. 1, showing amodification -thereof Figs. 3 and 4 are views showing another modification, Fig. 3 being a side, and Fig. 4 a. front elevation thereof; and

Figs. 5 and Gare views showing still anl other modification of the invention, Fig. 5

1921. Serial No. 466,487.

being a longitudinal section, and Fig. 6 an end elevation.

Similar characters of reference designate similarparts in each of the several views.

The lamp illustrated in Fig. 1 comprises a bulb 1, which is mounted in a base 2 which 1s arranged to cooperate with a bayonet socket of the type well known in t-he art. Obviously, any othertype of base and socket may be employed. The rear wall aof the lamp is in the shape of a paraboloid, and the filament 3 is carried on a filament support 4 having such length and position that the center of the filament is at the focal point of thc paraboloidf This filament is as com pact as possible, and may be of any known kind, whichl approximates the ideal condition of a pointsource of light. The interior or exterior surface of portion a is silvered, and serves, therefore, to reflect the rays of light from source 3 and to form them into a substantially parallel beam of light which passes through the non-silvered part of the bulb. A shield 5 of opaque substance is shown mounted in the interior of the bulb where it\is supported by means of wires 6 extending from the filament support 4. The shield is illustrated as being substantially convex in shape and of such size as to prevent direct rays of light from passing out of the bulb,

so that only the parallel beam of reflected.

liglit'is emitted' therefrom. If desired, Athe shade 5 may be made of colored or other translucent material so as to permit the direct' rays of light to pass out4 of the bulb after they have been so reduced in intensity that they will cause no glare.

The lamp illustrated in Fig. 2 is similar to that of Fig. 1 exceptthat the base is at right angles to the axis of the bulb. In this ymodification, a filament support 4 extends through acylindric-al recess 7 in the reflect'- ing portion a of the lamp bulb. Shield 5', moreover, is directly mounted on the filament support 4. f

Figs. 3 and 4 show the invention in its preferred form of embodiment. In this modia horizontal axial position, extending into v the bulb from the `forward. or ytransparent portion b of the bulb. A shield 5 isshown as being integral with the support 4, the surface 10 of the support being for this purpose coated with opaque or colored paint although any other suitable method mayl be emtranslucent.

ployed for rendering the vshield opaque or The reflecting surface a of the bulb is shown as provided with an enlargement 11 preferably unsilvered, which serves primarily for increasing the heat radiating capacity. The base of the bulb is mounted in a socket carried on an arm 15 which is pivoted on the bolt or rivet 16 and passes between the members 17 which are parts of the frame in which the lamp is supported. The lower end of the arm 15 is bevelled, as shown, and co-acts with a blade spring 18 which serves to bias the same in counterclockwise direction. A stop 19 limits the extent of movement of arm 15 and a screw 20 is provided on arm 15 to cooperate with the stop. By means of this arrangement, the elevation or depression of the beam of light emitted from the lamp may be adjusted closely. This feature is particularly valuable when the lamp is used on automobiles or other vehicles, where it is important that the beam shall not exceed a given height, so as to prevent objectionable glare.

When a filament of the lamp burns out, a new lamp may be conveniently mounted in the socket by swinging the arm 15 downwardly against the pressure of spring 18 until the bevelled portion of the arm engages the surface 21 of members 17. at which time the arm is substantially horizontal so that the whole lamp may be conveniently removed and a new one substituted therefor.

It will be understood that the lamp and its mounting, as illustrated in Figs. 3 and 4, is preferably enclosed in a casing having a removable front which may be of plain glass. The casing serves to protect the lamp from breakage and from dirt, and is of particular importance when the lamp is used as a head light for an automobile or other vehicle.

It will be observed that although part of the light is obscured, owing to the mounting being placed in the front of the lamp, the practical effect of this is negligible, owing to the intensity of the light.

In manufacturing the lamps, the bulbs are preferably blown in moulds shaped in accordance. with the distribution of light to be derived from'the lamp a. and the filaments are thereupon centered relatively to the focal points of the reflecting portions of the bulbs. In place of the filament type of lamps it is possible to use lamps employing other sources of light, as for example, the enclosed tungsten-arc lamp, which is particularly suitable lfor certain applications, owing to the concentration of the light at a single point. Although the reflecting surfaces have heretofore been vdescribed as being paraboloids, it

- will be readily understood that other suitable shapes may be employed, as for example, a shape which will cause the beam to spread in a lateral direction so that when the lamp is used as a head light, the beam A:is spread over a wide area of the road. It Will be understood that the proper shape suitable for any particular purpose may readily be designedn by graphical methods in accordance with the well-known laws of optics. An important advantage of this method of making .the lamps is that any shape may be readily and accurately reproduced by using properly shaped moulds.

Although in each of the above-described embodiments of the invention a shield is mounted inside the bulb, it is to be understood that this shield may be omitted, if desired. Such an embodiment of the invention is illustrated in Figs. 5 and 6, where 30 is the lamp provided with a paraboloid reflecting surface a at the focus of which is mounted the filamentl 3. The lamp is mounted in a socket 31 fixed in the rear end of a sheet metal casing 32. The interior surface of this casing is painted preferably a dead black so as to-be substantially non-reflecting. Across the forward end of the casing is placed a shield 33 of opaque, colored or translucent material, the lower edge of which is in substantially horizontal alignment with the filament, as indicated by the line 34, so that no direct rays of light emanating from the filament can pass above the horizontal plane. The reflected rays, moreover, are substantially parallel and tilted downwardly, owing to the slight inclination which is given to thelamp 30. .The result of this is that no light passes above the horizontal so that there can be no glare above the level of the lamps. When, therefore, the lamps are used as the headlights of an automobile or other vehicle, the road will be intensely illuminated but all glare will be avoided. 'The marked advantage which this form of embodiment of the invention in common with other forms, has over the headlights now common in the art, is the absolute flxedness of the filament relatively to the reflecting surface, so that the reflected beam of light has a fixed form of cross-section, which does not vary, owing to the impossibility of moving the filament relatively to the reflecting surface. This fixedness does not exist in the present headlights and the light emitted by them will consequently vary in direction, thus producing glare in spite of all other precautions.

Another advantage which the projecting device of my invention has over those noW common in the art, particularly the type in which a separate reflector is mounted behind a lamp bulb, -is the absence of a multiplicity of reflecting and refracting surfaces, such as the inner and outer surfaces of the lamp bulb, by which surfaces part of the light is reflected and refracted a number of times before it can pass out of the headlight, with the result that the beam loses its intensity and sharp definition. In the projecting lamp of my invention, there is but one reflecting surface, particularly, if the silvering is applied to the inner surface of the bulb, so that little or nothing of the above-described eff l ward part of its surface in the shape of a paraboloid, a concentrated source of light `comprising a filament located Within said bulb substantially at the focus of the said paraboloid, means for rendering the said parabolic portion of the surface of the bulb reflective to the light from said filament, the remaining surface of the bulb permitting the light to pass freely out of the bulb, a support for said filament, a base in which said sup,- port is mounted, said support and base being disposed forwardly of said reflecting surface, and serving as a shield for the rays passing directly from said filament source.

2. In a lamp, a glass bulb, a concentrated source of light located Within said bulb, said bulb having a portion of its surface treatedV to reliect light from said source, and a shield interior to said bulb for preventing the direct rays of light from passing out of said bulb.

3. In a lamp, a glass bulb, a concentrated source of light located Within said bulb, said bulb having a portion of its surface treated to reflect light from said source, and a shield interior to the bulb located in the path of' the rays passing direct from the filament to the exterior of the bulb, but not in the path of the reflected rays passing out of thel bulb.

4. In a lamp, a bulb having rear reflecting and front transparent surfaces, a source of light Within said bulb, and means interior to the bulb for intercepting the path of the direct rays substantially coaxial to the bulb Without intercepting the path of a substantial part of the rays passing from the reflector to the exterior of the bulb.

5. In combination, a bulb consisting of refleeting and transparent portions, the said transparent portion extending across substantially the entire front of the bulb, a source of light and a shield interior to the bulb said shield being constructed so as to intercept rays of light coaxial to the bulb, said reflecting portion of the bulb, the source of light and the shield being so placed With reference to each other, thatsubstantially no direct light passes out of the bulb.

' 6. A lamp comprising a bulb, said bulb comprising a rearward reflecting and a forward transparent surface, a concentrated source of light Within said bulb, and a shield interior to said bulb for permitting the direct rays o f light to fall on substantially the entire reecting surface and for preventing substantially all the direct rays from being emitted.

7. A lamp comprising a bulb, a concentrated source of light within said'bulb, a portion of said bulb being arranged to refleet the light from said source in a beam of predetermined direction and a shield mounted inside said bulb for eliminating substantially all of the light passing directly from said source in the directionof said beam.

8. In combination, a bulb having part of its surface in the shape of a paraboloid; a concentrated filament within said bulb, said filament being located at the focus of said paraboloid, and a stationary shield interior to the bulb' for materially reducing all light directly emitted 'from said lilament,-except such as. is reflected from said paraboloid surface. I

9. In a unitary lamp structure, a reflector, a concentrated source of light and means interior to the bulb for eliminating substantially all the centrally direct rays from the source and yet permitting the emission of a beam of indirect light substantially parallel to the axis of the reflector of said lamp.

10. In'a unitary lamp structure, a bulb, a concentrated source of light therein, a reflector integral With the bulb, a stationary shield interior to the bulb and directly in front of the filament and being of such a form that it intercepts the centrally direct rays of the lamp but permits the remainder of the light to distribute itself uniformly over substantially the entire reflector.

11. In a lamp, a glass bulb having a rearward part of its surface in the shape of a paraboloid, a concentrated source of light' comprising a filament located Within said bulb substantially at the focus of the said paraboloid,whereby said rays emerge from the bulb substantially parallel, means forrendering the said parabolic portion of the surface of the bulb reflective to the light from said filament, the remaining surface of the bulb permitting the light to pass freely out of the bulb, a support for said filament, said support being integral with said reflect- Iing ,surface whereby said filament and surface are immovably fixed with reference to one another.

In testimony whereof I have aliixed my Nsignature to this specification.

.HEREWARD LESTER COOKE.' 

